Design of stable and reactive vanadium oxide catalysts supported on binaryoxides

A series of titania based mixed oxides viz., TiO2-SiO2, TiO2-Al2O3, TiO2-Zr O2. and TiO2-Ga2O3 were prepared by a coprecipitation method. These mixed o xides were impregnated with V2O5 ranging from 2 to 30 wt% by using ammonium metavanadate as source of vanadium oxide. The mixed oxide supports and the vanadia impregnated catalysts were then subjected to thermal treatments fr om 773 to 1073 K and were investigated by XRD, FTIR, O-2 uptake and BET sur face area methods to establish the effects of vanadia loading and thermal t reatments on the surface structure of dispersed vanadia species and thermal stability of the catalysts. Calcination of coprecipitated support hydroxid es at 773 K resulted in the formation of an amorphous phase, and further he ating to 1073 K resulted in the formation of titania anatase phase, except with TiO2-ZrO2 support where a ZrTiO4 compound was observed. All these mixe d oxides exhibited a high thermal stability. Oxygen uptake results suggeste d a high dispersion of vanadia on these mixed oxide supports when calcined at 773 K. The mixed oxide based V2O5d catalysts studied are found to be ver y active and selective for the synthesis of isobutyraldehyde from methanol and ethanol, and for the selective oxidation of 4-methylanisole to anisalde hyde. (C) 1999 Elsevier Science B.V. All rights reserved.